The present invention relates to manually-operated self-inking stamping devices of the type having a self-inking stamp pad for impressing any suitable surface with a printed message, design or the like.
Typical prior art stamping devices of the above type utilize a base member for receiving and storing therein the stamp pad and a depressable handle affixed to the stamp pad for effect-contact of the stamp pad with the surface to be stamped, and a biasing arrangement for normally urging the stamp pad upwardly within the base member. The handle may accordingly be depressed against the urging of the biasing arrangement to cause the stamp pad to contact the surface to be stamped. While these devices provide generally satisfactory printing results, they suffer from the disadvantage that the stamping pressure exerted in depressing the handle cannot be uniformly regulated. When the self-inking stamp pad is relatively new, and therefore has an ample supply of ink retained therein, only a light depressing force on the handle is necessary to effect satisfactory printing. However, when the stamp pad has been in use for a considerable length of time, a relatively greater depressing force must be exerted on the handle to achieve comparable printing. The accurate regulation of the depressing force necessary to achieve uniform printing results throughout the useful life of the stamp pad is not possible with such prior art stamping devices.
Other prior art stamping devices of this type have employed various means allowing selective adjustment of the distance which the handle may be depressed thereby facilitating regulation of the stamping pressure exertable upon depression of the handle. One such prior art device is disclosed in U.S. Pat. No. 4,022,127, and employs a two-part bushing disposed below the handle of the stamping device and about a shaft extending from the handle to the stamp pad to act as a stop to restrict vertical depression of the handle, the two bushing parts being threadedly connected so that the length of the entire bushing unit is variable by rotation of the respective bushing parts thereby varying the distance which the handle may be depressed.
Another known prior art device utilizes a cam unit having a sloping cam surface disposed to act as a stop for the handle, the cam unit being either rotatable or slidable to vary the effective height of the cam surface thereby regulating the distance which the handle may be depressed. Such a stamping device is disclosed in U.S. Pat. No. 2,900,902.
In the stamping device of U.S. Pat. No. 4,203,362, the handle is threadedly mounted on a shaft extending from the stamp pad through the base of the device to permit rotational positioning of the handle along the shaft, a movable locking member extending between and engaging the base and the handle in normal operation to maintain the base and handle rigid with respect to each other and to act as a stop for the handle upon depression thereof. To facilitate adjusting positioning of the handle along the shaft, the locking member is initially moved manually to an adjusting disposition disengaged from the base member at which the handle may then be rotated about the shaft to vary the effective length thereof between the handle and the locking member thereby correspondingly varying the distance the handle may be depressed. Thus, in this device, adjustment of the position of the handle on the shaft requires a movement of the locking member along the length of the shaft to disengage the locking member from the base and subsequent rotational movement of the handle while maintaining the locking member disengaged from the base.